[PATCH] ftoastr: port to -Wdouble-promotion

[Paul Eggert]

Work around -Wdouble-promotion false alarm in recent GCCs.
* lib/ftoastr.c (PROMOTED_FLOAT): New macro.
(ftoastr_snprintf, FTOASTR): Use it.
---
 ChangeLog     |  7 +++++++
 lib/ftoastr.c | 11 ++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index c36d0de..a6f6b8b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2017-02-24  Paul Eggert  <address@hidden>
+
+       ftoastr: port to -Wdouble-promotion
+       Work around -Wdouble-promotion false alarm in recent GCCs.
+       * lib/ftoastr.c (PROMOTED_FLOAT): New macro.
+       (ftoastr_snprintf, FTOASTR): Use it.
+
 2017-02-21  Bruno Haible  <address@hidden>
 
        lock tests: Fix build failure on GNU/Hurd (regression from 2017-01-05).
diff --git a/lib/ftoastr.c b/lib/ftoastr.c
index 826340c..ef861e2 100644
--- a/lib/ftoastr.c
+++ b/lib/ftoastr.c
@@ -39,6 +39,7 @@
 # define FLOAT_MIN LDBL_MIN
 # define FLOAT_PREC_BOUND _GL_LDBL_PREC_BOUND
 # define FTOASTR ldtoastr
+# define PROMOTED_FLOAT long double
 # if HAVE_C99_STRTOLD
 #  define STRTOF strtold
 # endif
@@ -48,6 +49,7 @@
 # define FLOAT_MIN DBL_MIN
 # define FLOAT_PREC_BOUND _GL_DBL_PREC_BOUND
 # define FTOASTR dtoastr
+# define PROMOTED_FLOAT double
 #else
 # define LENGTH 1
 # define FLOAT float
@@ -55,6 +57,7 @@
 # define FLOAT_MIN FLT_MIN
 # define FLOAT_PREC_BOUND _GL_FLT_PREC_BOUND
 # define FTOASTR ftoastr
+# define PROMOTED_FLOAT double
 # if HAVE_STRTOF
 #  define STRTOF strtof
 # endif
@@ -77,20 +80,21 @@ static int
 ftoastr_snprintf (char *buf, size_t bufsize, char const *format,
                   int width, int prec, FLOAT x)
 {
+  PROMOTED_FLOAT promoted_x = x;
   char width_0_buffer[LENGTH == 1 ? FLT_BUFSIZE_BOUND
                       : LENGTH == 2 ? DBL_BUFSIZE_BOUND
                       : LDBL_BUFSIZE_BOUND];
   int n = width;
   if (bufsize < sizeof width_0_buffer)
     {
-      n = sprintf (width_0_buffer, format, 0, prec, x);
+      n = sprintf (width_0_buffer, format, 0, prec, promoted_x);
       if (n < 0)
         return n;
       if (n < width)
         n = width;
     }
   if (n < bufsize)
-    n = sprintf (buf, format, width, prec, x);
+    n = sprintf (buf, format, width, prec, promoted_x);
   return n;
 }
 #endif
@@ -106,6 +110,7 @@ FTOASTR (char *buf, size_t bufsize, int flags, int width, 
FLOAT x)
      <http://dx.doi.org/10.1145/1809028.1806623>; also see the
      2010-03-21 draft <http://florian.loitsch.com/tmp/article.pdf>.  */
 
+  PROMOTED_FLOAT promoted_x = x;
   char format[sizeof "%-+ 0*.*Lg"];
   FLOAT abs_x = x < 0 ? -x : x;
   int prec;
@@ -128,7 +133,7 @@ FTOASTR (char *buf, size_t bufsize, int flags, int width, 
FLOAT x)
 
   for (prec = abs_x < FLOAT_MIN ? 1 : FLOAT_DIG; ; prec++)
     {
-      int n = snprintf (buf, bufsize, format, width, prec, x);
+      int n = snprintf (buf, bufsize, format, width, prec, promoted_x);
       if (n < 0
           || FLOAT_PREC_BOUND <= prec
           || (n < bufsize && STRTOF (buf, NULL) == x))
-- 
2.9.3